1. Field of the Invention
The present invention relates to a performance monitoring facility in an asynchronous transfer mode (ATM) switching system, more particularly relates to line interface equipment in an ATM exchange.
An ATM switching system consists of a plurality of ATM exchanges connected for example in cascade via lines. In such an ATM switching system, for improvement of the reliability of the system, the performance, i.e., the transmission quality of each line, has been monitored by running monitoring cells of fixed lengths along the lines.
The present invention is directed to a monitoring facility in an ATM switching system for performing the above-mentioned monitoring operation.
2. Description of the Related Art
As will be explained in detail later with reference to the attached drawings, an ATM switching system to which the present invention is applied comprises a plurality of ATM exchanges and lines connecting them in cascade. Performance monitoring operation administration and maintenance (OAM) cells are transmitted through a plurality of lines from one ATM exchange to another. The transfer of the OAM cells allows the performance of the line from one exchange (point) to another to be monitored.
Conventionally, the performance monitoring facility to which the present invention is directed has been realized by a processor since its inherent function has been one which should be handled by a processor.
However, the amount of processing of messages transferred with the processor of an opposing ATM exchange by using the performance monitoring (PM) OAM cells is considerably large, so the load of the processor has become considerably heavy. For this reason, there is a problem that processing which should be handled by the processor other than the monitoring of the performance can no longer be carried out at high speed.
In addition to this, a high speed communication interface must be provided between the line interface equipment (L.cndot.INF) transferring the monitoring use OAM cells via the lines and the processor, that is, in an ATM switch arranged between the equipment (L.cndot.INF) and the processor, so there is a problem of an increase of costs of the ATM exchange.